The goal of this KO2 proposal is to allow the Principal Investigator to understand the role that fluid flow has on regulating key gene that control the morphology of developing heart valves, providing him with greater than 75% of time dedicated to his research over the next five years. Fluid flow has shown to be crucial for cardiac form and :unction. Alterations in fluid flow leads to various cardiac malformations including the cardiac valves. Specifically the Principal Investigator will focus on elucidating the effects that various flow parameters have on the morphology and gene regulation of key molecules in a unique 3-D model system established in the investigators laboratory. He will try to establish the mechanism that flow activates and where in the cascade of crucial signaling events fluid flow should be placed. The long term goal is to understand the importance of fluid flow n regulating the morphology of the developing cardiac valves. The knowledge gained from these experiments will create new strategies for the treatment of cardiac birth defects and valuable information concerning the design of tissue-engineered heart valves. A range of biochemical and cell biological studies on signaling mechanisms crucial to valve development are funded by NHLBI RO1 grant (HL072958-01). Stimulated by a new model system developed in the Pi's laboratory to study later stages of valve development which is amenable to directly studying the effect of fluid flow on valve formation, the Principal Investigator would like to expand the project to investigate this crucial question. The specific aims will test the hypothesis: that fluid flow in the heart regulates valvular morphogenetics and involves key signaling pathways. Our tenets will be tested in the following aims: 1) Determine the consequence of fluid flow on the differentiation and morphogenesis of valve leaflets;2) Identification of altered expression of structural proteins in the Jak-3 deficient developing valves under flow;3) Characterization of altered gene expression in endocardial cells exposed to fluid flow. As part of the KO2 project new. techniques will be introduced into the investigators already interdisciplinary laboratory. The Principal Investigator will undergo additional exposure to Rheology (study of fluid flow) and interactions with bioengineers and cardiovascular biologists will be expanded. The investigator has assembled a unique and dynamic group of investigators from which to draw upon. The Principal Investigator is well versed to answer truly fundamental questions regarding the role of fluid flow in regulating cardiac valve formation (End of Abstract)